code: def trained_model():
      estimator = LinearRegression()
      return get_regression_model_trainer()(estimator)[2]
  
file_path: m2cgen/tests/conftest.py
imports: import io
  import pickle
  import pytest
  from sklearn.linear_model import LinearRegression
  from tests.utils import get_regression_model_trainer, tmp_dir
label_desc: Use image node_id 4 for calling a global function with example usage: trained_model() and returns: get_regression_model_trainer